The present invention relates to composition and method for treatment of industrial waste water, for example from metal plating operations which commonly include chromic acid. Chromic acid of the waste water is considered toxic and must be treated for removal prior to introduction of waste stream into sewage systems.
In the prior art, waste water streams including chromic acid have been treated with chemical reducing agents to form trivalent chromium. This is followed by a treatment with alkaline materials to precipitate chromic hydroxide which is insoluble and can be removed from the effluent prior to introduction of the water into the sewage or waste water systems.
In general all prior art processes have required the pH of the water be first lowered with acid to facilitate the chemical reduction. The reduction reaction is controlled by measure of the oxidation-reduction potential. In another step the pH of the solution is then increased to precipitate the hydroxide. Such prior art methods have required at least 3 vessels, two pH monitors and one oxidation-reduction potential monitor.
Accordingly, prior art methods are expensive from the standpoint of capital investment and labor because of the multiple steps. Additionally. The need to monitor each step is subject to error and the inadvertent release of toxic material Additionally, the prior art methods are expensive because of the multiple chemicals required.
No prior art process is known wherein chromic acid can be easily and efficiently removed in a continuous process in a one step chemical reaction which is easily controlled.